Standing on the sidewalk we listen to the sound of the horn of a passing car.As the car passes us,the frequency of the sound changes from high to low in a continuous manner,that is,there is no abrupt change in the frequency heard.This is because
A)the pitch of the sound of horn changes continuously.
B)the intensity of the sound heard changes continuously.
C)we are not standing directly in the path of the traveling car.
D)All of the reasons contribute to the heard effect.

Question

Quizplus · Accepted Answer

The observed change in frequency from high to low as the car passes is due to the Doppler effect, which occurs because the relative position of the observer to the source of sound (the car) changes, not because the pitch or intensity of the sound inherently changes. Being off to the side (not in the direct path) of the car's movement is the relevant factor here; the pitch and intensity of the horn itself do not change.

Standing on the Sidewalk We Listen to the Sound of the Horn